Mumbai: The combined market capitalization (m-cap) of eight of the country's top 10 firms diminished by Rs 39,892.81 crore during past week, while state-run Coal India toppled Reliance Industries as the most valued company.

Coal India toppled Reliance Industries as the country's most valued company, ending billionaire Mukesh Ambani-led corporate giant's over four-year rein at the top of the market valuation charts.

With a market cap of Rs 2,48,675.09 crore as on Friday, Coal India added Rs 5,305.74 crore to its valuation last week. During the period, the share price of the company rose by over 2 per cent on the Bombay Stock Exchange (BSE).

Shares of Coal India have shown a remarkable surge ever since its listing on November 4, 2010. The company had raised over Rs 15,000 crore through its IPO, which gave it a market valuation of over Rs 1,50,000 crore.

RIL shares have been under pressure in the recent past, while ONGC and CIL have managed to outperform in a weak market on several occasions in past few days.

ONGC was at the third position in the market valuation charts at the end of Friday's trade. However, in late morning trade that day, the state-run company pipped RIL to emerge as the country's second-most valued company with a slightly higher market valuation, but could not retain the lead for the entire day.